This invention relates to adaptive communication for mobile router systems.
Providing radio communication services to a distributed set of clients can be challenging in the face of these clients moving in an environment and/or requiring varying communication capacity over a wireless medium, for example, for radio frequency communication over the air. One approach is to use a set of movable “routers” and to position those routers to satisfy the client requirements, or at least to approach full satisfaction of those requirements in a best possible manner according to an overall cost function that depends on the degrees to which the clients' requirements are satisfied.
In this description, the references to “routers” should be understood broadly as devices that route communication, without implication that they perform any particular type of processing or that they operate at any particular layer of a communication protocol stack. For example, in certain example that addresses wireless radio frequency data communication, the described routers function as WiFi access points (or repeaters) functioning at layer 2, and in other embodiments, the also router perform layer 3 functions. However, it should be understood that no particular processing of communication is essential for a device providing communication services to be considered to be a “router”. Similarly “client” should be understood broadly to be a communication node in communication with the router. For example, a client may be a computer, smartphone, or other fixed location or mobile device.
Examples in which positioning mobile routers can be important is in swarm robotic systems, which perform many complex tasks through coordination, such as cooperative search of an environment, consensus, rendezvous, and formation control. For example, Google's Project Loon, Facebook's Connectivity Lab, and similar projects envision using a network of controllable routers to provide wireless communication infrastructure in remote areas of the world. Beyond simply maintaining connectivity, reliable communication may include supporting heterogeneous and possibly time-varying communication rates amongst different pairs of agents. For example, some agents may need to use the network for transmitting video while others may simply wish to transmit status information.
The general problem of optimal placement of routers to service a set of spatially distributed clients has been address in previous work in Multi-Robot Coordination. Past work on this topic includes two classes of approaches.
The Euclidean Disk Model approach employs Euclidean disk assumptions where signal quality is assumed to be deterministic and mapped perfectly to the Euclidean distance between the communication nodes. A Euclidean metric allows for quadratic cost for the edges of the network and enables a geometric treatment of an otherwise complex problem. However, this approach can be limited because, in reality, signal strength suffers from large variations over small displacements.
More recently, efforts have focused on giving the communication quality over each link in the network a more realistic treatment by sampling the signal strength and building closed-loop controllers using this feedback. Stochastic Sampling Methods includes methods that either supplement theoretical models for signal strength with a stochastic component based on the collected samples, or use the collected samples to design stochastic gradient controllers However, in general, these approaches suffer inefficiencies associated with sampling, and associated router movement, needed to estimate the gradient, and suffer from local minimum problems inherent with such gradient approaches.
In other domains, direction of arrival information has been estimated for wireless clients using a variation of a Synthetic Aperture Approach, for example, as described in International (PCT) Patent Pub. WO2015/100237, titled “LOCALIZATION WITH NON-SYNCHRONOUS EMISSION AND MULTIPATH TRANSMISSION,” which is incorporated herein by reference. However, this or other approaches to acquiring direction or arrival information have not been applied to the problem of positioning mobile routers.